As the liquid supply device as described above, for example, Patent Document 1 discloses a writing instrument that stores liquid ink. In the writing instrument, a main body is provided with a partition, and the partition divides between an ink storage chamber that stores the ink and a reservoir chamber communicated with the atmosphere. A through hole is formed in the partition to insert a-rod-shaped ink supply material (relay core) made of a porous material, and a gap to hold the ink by capillary force is formed between the outer periphery of the ink supply material and an inner wall of the through hole.
The ink membrane held in the through hole breaks due to an increase or decrease in the pressure inside the ink storage chamber, and the so-called gas-liquid exchange action is obtained such that the ink flows into the reservoir chamber, the air flows into the ink storage chamber, and the like. Such gas-liquid exchange action is a preferable structure to compensate for changes in the ambient temperature and changes in the pressure inside the ink storage chamber. Further, when the ink is consumed by the writing instrument, the ink in a portion where the ink is held by capillary force is sucked out, the gas-liquid exchange action is performed in the portion, the sensitivity of ink supply to a pen material becomes excellent, and the writing instrument thus has a structure where light and shade is hard to occur in writing.
The publication further discloses a structure where the reservoir chamber is provided with a porous ink holding material made of cotton or the like, or with a feeder mechanism such that a number of gaps are formed continuously along the axis direction so as to hold the ink flowing out of the ink storage chamber due to changes in temperature and the like. By providing such an ink holding material or feeding mechanism, it is intended to effectively prevent the ink from leaking from the atmosphere communication hole to the outside and the like. The publication also discloses a structure for dividing the ink storage chamber by a plurality of partitions to reduce a drain of the ink to the reservoir chamber.
In relation to the writing instrument as disclosed in above-mentioned Patent Document 1, Patent Document 2 discloses a structure for increasing a return rate of ink flowing into the reservoir chamber. More specifically, the reservoir chamber is provided with an ink drain preventing member that divides the reservoir chamber while causing an ink supply material to be inserted into the preventing member with a predetermined gap, and thus is configured to return the ink flowing into the reservoir chamber on the pen side to the ink supply material.
In the above-mentioned well-known writing instrument, since the ink supply material is disposed in the center portion and the gas-liquid exchange is performed around the ink supply material (the gas-liquid exchange is not performed inside the ink supply material), the sensitivity of the gas-liquid exchange is improved, and it is possible to supply the ink inside the ink storage chamber to the pen side (application side) promptly. The ink is thereby supplied with high sensitivity even in writing at high speed, and advantages are obtained of enabling resolution of troubles such that a thin spot occurs, writing becomes impossible and the like.
However, there is a problem that the ink inside the ink storage chamber tends to flow into the reservoir chamber side due to the head pressure acting on a gap portion formed in the partition, changes in temperature, and particularly, changes in pressure by increases in temperature. In other words, the above-mentioned writing instrument is used under various circumstances that the temperature is varied, its position is varied and the like, and for example, when the temperature increases and the pressure inside the ink storage chamber increases, the ink flows out of the gap formed in the partition into the reservoir chamber. In this case, as disclosed in Patent Document 1, by providing the reservoir chamber with a porous ink holding material, it is possible to absorb the flowing-out ink and suppress leakage of the ink to the outside and the like. Alternately, also in the structure as disclosed in Patent Document 2, it is possible to prevent the ink from leaking to the outside, and to bring the ink flowing out of the ink storage chamber into contact with the ink supply material to return thereto.
Further, in the above-mentioned writing instrument, it is desirable in the appearance that the ink stored in the ink storage chamber in each writing instrument is maintained at a certain amount when a number of writing instruments are arranged to sell, for example. In other words, when the amount of the ink in the ink storage chamber is different between writing instruments of the same type, the sale is affected (a writing instrument with a small amount of ink in the ink storage chamber cannot be sold, or some store refuses to display such a writing instrument, and the like.)
Generally, in the above-mentioned writing instruments, a lapse of time differs (the season also differs) before the instrument is placed for sale in a retail store through the manufacturing process and shipment process, and the apparent ink storage amount may differ largely for each writing instrument by the ink flowing into the reservoir chamber due to various factors such as changes in temperature, changes in position and the like during the lapse of time.
Meanwhile, in the writing instrument such that the ink storage chamber is divided by a plurality of partitions, since each chamber stores the ink, it is possible to prevent the apparent ink storage amount from differing largely. However, dividing the ink storage chamber into a plurality of chambers increases the number of parts, makes the assembly process complicated, and increases the cost. Further, when a pigment-based liquid (mixture of solvent and pigment) is used, the need arises of storing a spindle for mixing in the chamber, and storage of the spindle in not preferable in terms of the cost. Furthermore, since a plurality of storage chambers is formed along the axis direction, it is difficult to perform the operation for refilling the liquid.
Accordingly, in the writing instrument (liquid storing device) with the above-mentioned structure, it is desirable that such changes in the ink storage amount are reduced as much as possible in a simple structure, while the above-mentioned advantages are maintained (such that the sensitivity of ink supply to a pen material is excellent, light and shade is hard to occur in writing, and the like.)
Patent Document 1: JP 2001-315483
Patent Document 2: JP 2004-50694